1. Department of Anesthesiology, University General Hospital Attikon,12462 Athens, Greece
2. Department of Anaesthesiology, Rea Maternity Hospital, 17564 Athens, Greece
3. Department of Anaesthesiology, General Hospital of Athens Alexandra, 11528 Athens, Greece
4. Department of Obstetrics and Gynaecology, General Hospital of Athens Alexandra, National and Kapodistrian University of Athens, 11528 Athens, Greece
5. 1st Department of Respiratory Medicine, Sotiria Thoracic Diseases Hospital of Athens, School of Medicine, National and Kapodistrian University of Athens, 11527 Athens, Greece